There are known devices for slot perforation of wells in the prior art that allow to simultaneously form at least two perforation slots in the production column, for example, as disclosed in the patents RU 2249678 C2, IPC E21B 43/112, 10.04.2005, RU 2371569 C1, IPC E21B 43/112, 27.10.2009, RU 2365743 C1, IPC E21B 43/112, 27.08.2009. The size of the cutting tools used in the above designs' cutting assemblies is close to the diameter of the casing of the perforator device, allowing to make perforation slots with considerable depth.
The disadvantage presented by this device consists in its applying a non-uniform force to the cutting discs, where one of the discs is driven directly by the extending mechanism having the form of a wedge-piston or a deflecting wedge, while the second disc is driven indirectly by a lever from the first blade which may have the shape of a balance-beam. In this case, the first cutting disc, which receives the driving effort directly, travels the maximum distance into the rock, while the second disc, located above or below the first one, is less effective resulting in the second slot potentially not reaching the required width or depth, and in case of a prolonged operation of the perforator and of the disc blade being in a substantially deteriorated condition the second slot may not appear at all.
The objective of the proposed invention is to equalize the effort applied to the cutting blades of a double-sided perforator in order to provide for uniform opening of the production column simultaneously in at least two projections to ensure that diametrical slots of the equally high quality are created.
The closest analogue to the proposed invention is the perforation device disclosed in the patent RU 2365743 C1, IPC E21B 43/112, 27.08.2009, which is assumed as a prototype.
The prototype device comprises a casing containing a spring-loaded piston-pusher with an axial central channel and two lateral radial channels with jet nozzle installed in them, and a retractable cutting tool in the form of two rolling discs, mounted one above the other, with the mechanisms for their radial extension and retraction, which includes a double-arm lever mounted on a movable central axis between two vertical rods mounted on a fork rigidly attached to the bottom edge of the piston-pusher, having the cutting discs installed on hinges at the arms of the said lever, and a fixed deflection wedge mounted on the bottom of the casing with a given angle of the working surface to the axis of the device and a guiding slit for the lower cutting disc, that interacts with the lower double-arm lever's arm during the piston-pusher's axial movement, while the cutting discs' return mechanism is implemented as side plates with guiding grooves installed between the casing and the lower double-arm lever's arm in parallel with the working surface of the deflecting wedge, which houses the ends of the shaft of the lower cutting disc (with a clearance).
The prototype's design has the following drawbacks:
1. The effort supplied to the cutting discs is uneven: the piston's momentum is firstly transmitted to the lower cutting disc through the deflection wedge and only indirectly, through the double-arm lever, to the upper cutting disc.
2. The quality of perforation of the column by the cutting discs varies between the two of them.
3. The discs wear out unevenly resulting, in case of prolonged operations, in an increase of the rig-up and rig-down operations in order to have the cutting discs replaced.